I realized a few years after school I had mostly forgotten elementary calculus.
I still had my textbooks (Apostol volumes I and II) and re-read them. Things were again right with the universe--I could do elementary calculus.
A few years later, I realized I had again forgotten it. I decided for variety to buy Spivak's "Calculus" and read that instead of reading Apostol for a third time. Yet again, I could do elementary calculus.
The next time I realized I had forgotten elementary calculus, I re-read Apostol again (although just Volume I). To try to make it stick, I did every exercise in the book.
I of course have since forgotten elementary calculus. I'm not sure if doing all the exercises made it last longer or if I forget it as quickly as I usually do.
The next time I decide to relearn elementary calculus, I think I shall first make sure I have a long supply of problems covering the entire subject, and then after I finish the textbook I'll do a few random problems a week so that I have to actually use the stuff.
I still had my textbooks (Apostol volumes I and II) and re-read them. Things were again right with the universe--I could do elementary calculus.
A few years later, I realized I had again forgotten it. I decided for variety to buy Spivak's "Calculus" and read that instead of reading Apostol for a third time. Yet again, I could do elementary calculus.
The next time I realized I had forgotten elementary calculus, I re-read Apostol again (although just Volume I). To try to make it stick, I did every exercise in the book.
I of course have since forgotten elementary calculus. I'm not sure if doing all the exercises made it last longer or if I forget it as quickly as I usually do.
The next time I decide to relearn elementary calculus, I think I shall first make sure I have a long supply of problems covering the entire subject, and then after I finish the textbook I'll do a few random problems a week so that I have to actually use the stuff.